On a Friday afternoon in June 1979, a well-dressed man with a Midwestern accent walked into the Elbert Granite Finishing Company in Elberton, Ga., and commissioned a monument "to the conservation of mankind."

The man identified himself only by the pseudonym Robert C. Christian and said he represented a "small group of loyal Americans who believe in God" who wanted to leave a message for future generations.

Although Christian wasn't from Georgia, he selected a site in Elberton for the monument and construction soon began to his specifications.

On March 22, 1980, the Georgia Guidestones were unveiled, and they've been drawing a steady crowd of visitors for more than 30 years.

Often referred to as "America's Stonehenge," the monument is a 120-ton relic of the Cold War built to instruct doomsday survivors.

Shrouded in mystery, the hulking granite slabs are engraved in eight languages — English, Spanish, Swahili, Hindi, Hebrew, Arabic, Chinese and Russian — that relay 10 principles for "an Age of Reason." Here's what is written there:

Let all nations rule internally, resolving external disputes in a world court.

Avoid petty laws and useless officials.

Balance personal rights with social duties.

Prize truth — beauty — love — seeking harmony with the infinite.

Be not a cancer on the earth — Leave room for nature — Leave room for nature.

The first commandment is the subject of much controversy, with many believing it's a license to cull the human population.

Since the monument's erection, it's been targeted by vandals who have painted over it, thrown epoxy onto the slabs, and once covered the entire structure with black fabric.

Locals tell stories of witchcraft taking place at the stones, and Elbert County resident Mart Clamp, whose father helped carve the granite slabs, says there have been instances of teenagers showing up dressed in black and toting buckets of chicken blood.

"To some, it’s the holiest spot on Earth," Hudson Cone, a former Elberton Granite Association employee, told the New York Times. "To others, it’s a monument to the devil."

In addition to the 10 guidelines outlined on the stones, the monument also has astronomical features that the mysterious R.C. Christian might have thought important to apocalypse survivors.

The center column has a hole that points to the North Star, there's a slot that aligns with the sun's solstices and equinoxes, and there's an aperture in the capstone that marks noontime throughout the year.

An additional stone tablet is set into the ground nearby, and it lists various facts about the guidestones. It also references a time capsule buried beneath the tablet, but fields on the stone reserved for the dates it was buried have never been inscribed. It's unclear whether a time capsule was ever placed in the ground.

But despite its many unique features, it's the secrecy surrounding the Georgia Guidestones that brings visitors from around the world to the small city of Elberton.

The identity of R.C. Christian is a secret that Wyatt Martin, the banker who acted as his agent, vows to take to his grave.

"I made an oath to that man, and I can’t break that. No one will ever know," he said.